Wednesday, August 11, 2010

Mondial Electrics

I probably know more about the Mondial 175 TV electrical system than anyone else in North America. I have had trouble with it for a couple years in Italy, and brought it back to diagnose and repair here in California. Somehow in the course of this I burned out the dynamo armature. Of course, lacking proper test equipment, I ended up using an oscilloscope to be sure this was the actual problem (actually the oscilloscope is remarkably useful with these vintage electrical systems). Here's a shot of the bad output from my broken dynamo.

After a bit of a search, a friend sold me a possible replacement armature... but it was going to require some machining to get it to fit. So I ended up having the original rewound by the helpful people at Eurton Electric.
So the repaired dynamo worked adequately for the 2009 Giro d'California... but the regulator was still not good. Another friend managed to get me a replacement in Italy. But both of these regulators are pretty crude mechanical devices. Essentially they have a set of contacts inside, and these contacts open and close if the voltage is too high or low. On the oscilloscope you can watch this, and the rather rough waveform that gets output. And the regulator, even with it's built in temperature compensation is very variable. Mine seem to vary by a couple volts... leading to under or overcharging (and boiling or destroying) the battery.
Unfortunately, you cannot use a typical regulator on a dynamo system. A dynamo is a DC generator, and puts out a substantial amount of "over power" to the regulator. It requires a switching type regulator to dissipate the power sensibly.
I finally found a replacement (and modern) regulator that may work well in this system. Apparently many old British bikes also used dynamo systems and they suffer the same problem. So I ordered one of those, a DVR2.
After waiting a couple weeks for delivery (some Internet problems at the factory), I finally received this last week. And I test fit it tonight. It does appear to work! Now I need to fit it a bit more properly and give it a more formal test run. Here is a pic of the mounted DVR2. Note it fits in a hollow in the underside of the tank, where the original was.

1 comment:

  1. I'll be interested to see how you get on with it Carl, I've got a couple of bikes that would benefit from something similar..